CLINICAL BIOCHEMISTRY DEPARTMENT

 SHORT SYNACTHEN STIMULATION TEST

INTRODUCTION

Tetracosactrin (Synacthen, Cortrosyn) is a synthetic preparation comprising the first 24 amino acids of ACTH. It stimulates the adrenal cortex to produce cortisol, failure to respond indicating impaired adrenocortical function.

This test is of value in patients with suspected adrenocortical insufficiency eg. Addison’s disease and also during the later stages of withdrawal and following total cessation of previous long-term high dose glucocorticoid drug therapy, including topical preparations.

This test can be used either as an in-patient or out-patient screening procedure.

PRECAUTIONS

Please refer to the Trust’s phlebotomy procedure for sample collection precautions.
Allergic reactions to tetracosactrin are a possibility, but rarely occur.

PATIENT PREPARATION

This test is should be carried out between 9am and 10am, where practical, as responses will decline later in the day. The patient is placed in a reclining position to rest for 30 minutes prior to the test. Smoking is not permitted.

PATIENT ON THERAPEUTIC STEROIDS

The cortisol assay is interfered with by therapeutic glucocorticoids (prednisolone / methyl prednisolone / hydrocortisone). Therapy with such steroids should be discontinued and substituted with an alternative steroid (e.g. dexamethasone, betamethasone) at an equivalent dose (see BNF section 6.3.2) at least 3 days before the test. 
Alternatively, glucocorticoids should be stopped for previous 18 hours prior to the test - Caution: withdrawal of glucocorticoids may be dangerous.

PROTOCOL

1.

Take basal venous blood sample (6ml SST tube – yellow top).
If a basal ACTH sample is required for storage, pending results of the Synacthen test, collect a 5ml EDTA tube (purple top) and transport to the laboratory immediately.

2.

250ug of Tetracosactrin dissolved in about 1ml of sterile water or isotonic saline is administered intramuscularly. (Tetracosactrin is marketed as Synacthen (Ciba) for Cortrosyn (Organon)).

3.

After 30 minutes a further blood sample is taken (6ml SST tube – yellow top).
4. A sample at 60 minutes is not recommended, unless the test is being performed afternoon / evening (6ml SST tube – yellow top).

Label the samples with patient details and actual time taken. When test is complete, send request form and all samples (except for ACTH - see above) to the Clinical Biochemistry Department as soon as possible.

INTERPRETATION

Following levels refer to 30 minutes sample:

Greater than 600 nmol/L: Suggests intact HPA axis and unlikely to be associated with adrenocortical insufficiency.

525 - 600 nmol/L: May be adequate response, but may be associated with a degree of adrenocortical insufficiency (e.g. may need hydrocortisone cover during stress). A repeat test (especially if not performed in the morning) after at least 5 days may be helpful; adrenal antibodies may be useful if autoimmune adrenal disease suspected.

Less than 525 nmol/L: Adrenocortical insufficiency likely, requires endocrinologist assessment.

Reviewed by: Tony Everitt, Consultant Biochemist
Last edited 07/08/08